A wireless local area network (WLAN) enables wireless Internet access at home or offices or in specific service areas using portable terminals on the basis of radio frequency technologies. When there are too many stations (STAs) in a WLAN, probability of collisions happening between STAs in a channel access process increases. STAs which perform channel access without listening to a beacon signal may be in contention with other STAs allocated slots in the channel access process, and such contention may deteriorate efficiency of the entire network.